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Dairy cows produce milk for 10 months after they give birth to their calves, and they must be milked every 12 hours. On average a single cow produces 6.5 gallons of milk every day from two 10-minute milkings using mechanical vacuum machines that are attached to their udders. Imagine this routine taking place 9 million times every day. (There are about 9 million dairy cows in the U.S.)

While still at the dairy farm, milk is pumped along stainless steel pipes into a tank that chills the milk to 38°F or less. The fluid is constantly agitated to stop the cream from separating and to keep the temperature constant.

Every 24 to 48 hours, insulated trucks that hold up to 5,300 gallons transport milk from dairy farms to the processing plant. Once the tankers arrive at the plant, the milk has its temperature taken - if it’s above 44°F, the entire container is discarded, and another sample is tested for bacterial load. The milk is then graded, and pumped into the processing facility.

Historically, two grades of milk were established: Grade A and Grade B. The grade given depends on the milk meeting certain sanitary or quality standards. Grade A is for use in fluid milk products as well as any other dairy products, whereas Grade B which meets slightly lower standards, can only be used for manufactured dairy products, like cheese. Today, almost all the milk produced in the U.S. is Grade A.

The raw milk, regardless of what type of fluid product it’s destined to end up as, passes through a separator which spins the milk through a series of conical disks. This removes debris, sediment and some bacteria. But it also separates out the fat, splitting the contents into a cream portion that is 40 percent fat, and skim milk that is less than 0.01 percent fat.

The skim milk is drained away, then, has precise quantities of fat returned back to it, or not, depending on whether it's going to remain as skim milk, or become 1 percent, 2 percent, or whole milk which contains between 3.25 percent and 3.4 percent milk fat based on the processor’s formula.

What happens to all the excess fat? It gets turned into butter or processed into cream or ice cream.

Once milk has been calibrated just so, it's then pasteurized to destroy pathogens as well as spoilage bacteria and rancidity-causing enzymes that can shorten the shelf life of milk. The most common method used is the high-temperature, short-time (HTST) process in which constantly flowing milk is heated to approximately 161°F and held there for 15 seconds before being rapidly cooled.

If you thought this was the entire extent to which milk is processed, you’d be wrong. It’s then usually homogenized before being pumped into plastic jugs or cardboard cartons. This process is what stops the cream from separating again and floating to the top while milk sits on a grocery store shelf or in your fridge.

Milk naturally contains non-uniform globules of fat. It’s this lack of consistency in the size that causes the fat particles to rise to the top creating a “creamline”. To prevent this, milk is forced under extreme pressure and at high velocity to pass through tiny passages by a piston pump. This causes the fat particles to break up into countless, much smaller, identically-sized particles that are too miniscule to separate from the rest of the milk ensuring a smooth consistency for the duration of the product’s shelf life.

I don’t mean to suggest that milk is bad or any less nutritious because it’s been processed. But, let’s be clear, it is a processed food. The white stuff that comes out of a plastic jug is undoubtedly physically changed and compositionally altered from the white stuff that flows forth from a cow’s udder. As for the question as to whether whole milk is any more “natural” than skimmed or part-skimmed milk, the answer is a definitive NO.